Method of reproducing electrical oscillations and apparatus therefor



Jan. 8, 1929.

n H. KONHEIM METHOD OF REPRODUCING ELECTRICAL OSCILLATIONS AND APPARATUS THEREFOR Filed ost. 29, 1926 .Milly/).7

umg..

cies which does not include the natural period 'Patented Jan.. s, 1929.

UNITED STATES 'PATENT oF-rica. j

I' mam Kennern, or New Yorin, n. Y."

xEriroD or -nnrnomrcme Aiiniic'rmaar. osciLLATroNs AN'D arrana'rus 'r-Hiiniaron.

Application led 0ctoher29, 1926. Serial No. 144,990.

4 Y My invention `relates to the artof electrical l reproducers and deals more specifically with a. loud speaker system./

It is an obj ectof my invention to provide a loud speaker device which'will respond equally throughout the range of audible frequencies.

It isa further objectv of my invention to provide a loud speaker device' which is supn plied with oscillations of a band of frequenof the loudspeaker device.

Further it is an object of my invention .to provide a plurality of loud speaking units each of which is responsive-primarily 'to a p separate portionof the audible spectrum of frequencies.

Further it is an object of my invention to provide a plurality of selective amplifiers each of which is designed toemphasize certain separatev portions-of the audible spectrum. v

And it is a further object of my invention f to provide a loud speaker device with a filter to limit the range of frequencies supplied to the loudspeaker device.

-'I 'hese and otherobjects of my invention will be apparent readily to lone skilled in the art from the following description taken in connection-with the accompanying drawing Figure 1 showsa lr'haracterist-ic of an ideal loud speaker device.

' Figures 2 and '3 show characteristics of the `usual t pe of loud speaker-devices, having a natura resonant frequency at the' lower and the upper portion of the audible spectrum, re-

' spouse of emanating aan@ for. 11 of ai spectively.

" Figures Ltand 5 show. certain'characteristics of the ampliiiers embodied infiny inven-` tion.

Figure 8 :shows the' resultantlrcharacteristic Figure 9 .israfdi my invention: In rder to obtain good I of characteristic 'such as shown in" Figure 1j. That is, it is .necessary to obtain an even r'e- Figuressamir'showfheicharwiicsff the loud-511323103?.` devices. 'when operated 'by fthe amplifiers-embodied ing-my invention. 'l tionfof the fr ueiic For the fre uencies etlll y A aminatic yiewishowingL a complete radio embodying frequency. within lthe audible spectrum and when the frequencies to be reproduced approach the natural period of the loud speaker there is an unnatural and artilicial overemphasis of thesefrequencies, which results in a bellowing and distortion of the sound emitted. Many attempts have been made to. construct an aperiodic loud speaker `which attempts have Ilot'been wholly successful.

Iovercome this undesirable effect by prov viding a plurality of loud-speaker units each of. which has a natural period of vibration at points widely removed from each other in the audible spectrum, such as. shown, for example, in Figures 2 vand 3 of the drawing. Each of these loudspeaker units is then supplied with` e lectricaloscillations from a separate 80l amplifying unit, which is of the selective type and which is designed'to emphasize one portion' of the audible spectrum, while it suppresses frequencies in the reniaining portion ofthe spectrum. These amplifiers have the characteristics such as shown in Figures 4 and 5 of the drawing. Thus an amplifier having the characteristic shown in-Figure 1 .will suppress the lower portion and emphasize the upper portion of the audible spectrum; vwhile an amplifier having the characteristic shown in Figure' will emphasize-the lower portion and suppress 'the upper portion l* of the audible spectrum.

Asa. result of this combination o-ampliian fiers and loud speaker units each loud speaker device is designed to reproduce all `the frequencies over a portion only of the spectrum in .which its responsmis a'straightline func-4 whichinclude e natural-period of t e loud speaker,v however, the response is made sli ht due to the selective feature of the ampliv er. Y i A'Ioudf'speaker device having a characteristic Aof the-type shown in Figure 3 when operated-by amplifier having a characteristic of the type 'shown in Figure 5 will give a characteristic suchv as shown Figure l. Similarly 'a characteristic such as shown in a loud speaker device haymg the character- -1 i istie show-nin Figure 2 by means of an ampli- 'Y Figure 6 will be obtained by the operation of cov 7o would eliminateq this resonant eli'ect but these v ierlhaving the characteristic shown in Figcomplete Asystem embodying my invention:

Incoming radio signals may be intercepted at 11 and impressed upon the tuned circuit 12 of the vacuum tube 13 which acts as a ra dio frequency amplifier. Coupled to the tube 13 at 14 is a detector 15, the output of which is cou led to the amplifier 17 b means of the trans ormer 16. The details o this receiving equipment is not at all important for the purposes of the presentinvention and any other well known radio receiving system may be substituted therefor. Alternatively locall produced oscillations such as those of an e cetro-ma etic pic up or other electric phonograp devices may be substituted for the radio yreceiver. The selective amplifiers indicated generally by A and B are coupled to. the out ut circuit ofthe amplier 17 by means of t e transformers 18 and 19 respectively.. Rheostats 20 and 21 are provided as a convenient means o'f apportioning the amount of energy which will be supphed to primaries of the respective transformers 18 and 19.

I will now describe in detail the 'selective amplifiers which are designed to am ify one portion of the audible spectrum an suppressthe remainingportions of the au ible 'Spec The three internalimpedances of tube 29.

for example are;

1. The impedancebetween grid and-filament, commonly referredto in the-art'as RG,

is the internal impedance of.J the tube.

l2. The impedance between the filament and plate is the internal output resistance, commonl referred to as RP.

, 3. he capacity betweenv grid 'and plate, commonly referred to as the inherent capacityo'f-thetube...v i Y l I utilize a combination of the six impedancejs listed above to obtain selective am l1- a'tion. Thus, foreach stage, the-.amp car -tion will be a maximum when the cou ling the input -circuit of the vacuumtube 25. In

the output circuit of the vacuum tube 25 I provide the choke coil 26 which is of a low impedance. The coupling condenser 27 is of relatively small capacity. The vacuum tube 29 is coupled to 25 through the condenser 27, n

and the input circuit of the tube -29V is provided with the grid-return 28. In the output circuit of the tube 29. I also providea choke 30 and condenser 31 both of which have the same properties as the elements 26 and 27 Vrespectively. In the output .circuit of the tube` 29 I also connect the filter 32 which may consist of any suitable net-work of inductances and capacitances for the purpose of checking Y any undesirable electrical oscillations in the reproducing unit 33. The output of the reproducer 33 is conducted to lthe horn- 35 through the passage 34. o A

This amplllier has its selective characterl istie for the following reasons When the electrical'oscillations of varying frequencies are impressed. upon the transformer 18 amplification will start only whenv frequencies hi'gh enoulglh to .find

mately as great or greater than the ate impedances of theamplifying tubes, 1Jand also when the conductivity of the condensers is about as great `or eater than that of the grid-return 28. us the system A'wills l the im- Y pedance of the choke lco s 26 and 30 a Vproxiamplify only -those fr uencies which are above a redetermined vague.

In or er to amplify the lower portion of the audible spectrum I providethe amplifier B which has the vacuum tube 45 coupled to the common source of electrical oscillations of the amplifier 17, by `means of the transformer 19. In the. output circuit of vthe vacuum tube 45, I provide the choke coil 46 and the parallel condenser 47. The vacuum tube 51 is connected to the tube 45 through the large condenser 48 and choke coil 49. Tube 51 is provided wat the grid-return 5o.

vide the choke 52, condenser 53 and large condenser 54 all of which have the -same properties as the previously described elements 46, 47 i and 48, respectively. In the out ut circuit of the tube 51 I also 'connect the, ter

In the output circuit of the tube 51 I pro- 55 which like filter 32 is designed' to suppress undesirable fi-equencies, and to the filter 55 I' connectthe reproducing unit 56, which feeds its outputinto theloud'speaker 35 thro h the assa 57. Y

Thuegampliger Bglias its featurev of selectivity for the following reasons: A .l

The choke coils 46v and 52 are p to block. all audio frequencies:- jeiectively;f

The coupling condensers .48- and 54`a`re l of i,

ffrequencies varying `from the lower limit fofl audibility to the higher limit of audibility,

high capacity and are .designed to practically fthe combination of an 4amplifier comprising short circuit all audio frequencies.- The 'al chokes 46 and 52 are bypassed by small condensers 47 and 53 )which provide a pathfor the oscillations of the hi her frequencies* Inv the grid circuit of the tu e 51 the small choke 49 blocks the higher frequencies. This system 'will amplify, therefore, only signals of a frequency low enough to find anim edance 4about as great-'or greater than the p ate imstructure it is to be understood about asgreat or gre grid-return 50.

pedance of the tubes 45 and '51 inthe condensers 47 and.53,f..respectively, and which will find through the choke 49 aconductivity ter than that of the While I have disclosed a specific amplifier .thatl such amplier is merely-shown for the purposes of illustration of the invention, modifications of the same may be made by any' one skilled in the art without departing from vthe s irit and scope of this invention asdefined y the appended claims.

Having thus described my invention s I claim: 1. An amplifier' for` electrical impulses comprising in combination, a first unitconstructed and arranged to amplify comparatively slightly electrical impulses having a of said units, each of said amplify comparatively greatly another and to band of said frequencies, a second unit constructed and arranged Vto amplify eatly said impulses which said first mentloned unit fies slightly and to amplify slightly said impredetermined band of frequencies fies greatly, and separate acoustic devlces associated with each of said units.

2. An am lifier comprising in combination, a plurality of selective amplifying units, each of said units being designed to emphasize a predetermined ran e of frequencies and to suppress all `other equencies, and a separate acoustic device associated with each devices havin a natural period of vibrationwhich is outside of the range of frequencies which its' asso-` ciated unit 1s designed to emphasize.

3. In a radio receiving systemmeans to convert electrical oscillations of varying fr;-M quencies into sound impulses 'whlch comprises, a first unit adapted to amplify`os cillations of certain frequencies and to s uppress oscillations, of other frequencies, a second unit adapted to amplify oscillations of a frequency which said first unit is, adapted to suppress andto su press oscillations of a frequency which sai' first unit is adapted ,to amplify, and separate acoustic -devices associated with each of said units. 4. In a radio receiving system adapted to lurality of selective amplifying quency'range to a higher degree than any other of'said frequencies, and separate acoustic devices associated with each of said units -te 4convert the electrical impulses amplified thereby into sound vibrations. i -5. f In a radio receiving system. adapted to reproduce electrical impulses having a range offrequencies varying fromthe lower limit 'bf audibility to the higher limit of audibility, the combination of an amplifier comprising a plurality,v of selective amplifying units, each of said units being designed to am'- lify a` separate predetermined band of sai frequency range to a higher degree than any devices associated with each of said units to convert the electrical impulses amplified thereby into sound vibrations, and means-interposed between each unit and its associated acoustic device to permit the passage there'- and'that many other of said frequencies, separate acoustic 85 I between of impulses of predetermined frequencies only.-

6. vIn la system for repoducing electrical oscillations, a vacuum tu amplifier having an output circuit, a first selective amplification unit coupled to said output circuit and arranged to amplify comparatively slightly electrical impulses having a predetermined band of frequencies and to amplify comampliparatively greatly another band of Said fre-v 100 'quencies, a second selectiveampliicationunit pulses which said first mentioned umt ampll- 'coupled to said output circuit and arrangedx second coupling device, both said devices be- 'ing connected in parallel in said output circult, a first unit coupled to one of said del vices adapted t amplify oscillations `of cxar-A tain. frequencies and to suppress oscillations of other fre u'encies, a second unit'coupled to said other. evice adapted to am lify oscillations of a frequency which sai first unit is adapted to ,suppress and to slp ress 0SCillatians of a Nfrequencywhich sai Erst unit is adapted-to amp ify, and separate'm'eans conl nectedfin series with each ofsa'id devices sevlectiiel to vary theii'immt of energy trans- Y komm.

ferredy said cou to said units. 

